Artificial line.



B. S. HOYT.

ARTIHClM. LINE.

mwucmqu firm um. 24. 1911.

1,240,213. Patentedfiept 18, 191?.

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INVENTOR ATTORNEY R. S. HOYT.

ARTIFIQlAl. HNL APPucmou FILED IAII. 24. m1.

Patented Sept. 18,1917.

A'ITORNEY H. S. HUYT.

ARTIFICIAL LINE. APPLECATHIN HLED MN 24 19H.

1,240,213. 1 Patented Sept. 18,1917.

4 SHEETFSHEET 3.

NEb QQ ATTORNEY k v'u lx R. S. HOYT.

ARTIFICIAL LINE -APPLICATIOII mm mm 24. Ian. I

Patented Sept. 18, 1917.

4 SHEETS-SHEET 4- @mwm'qmm INVENTOR ATTORNEY BAY B. HOY'I, O! BROOKLYN,

TELEGRAPH COMPANY, A CO NEW YORK, ASSIGNOR TO AMERICAN TELEPHONE AND BIPORATION OF NEW YORK.

ARTIFICIAL LINE.

Application filed January 24, 1917.

To allwhom it may concern:

Be it known that I, RAY S. HoY'r, residing at Brooklyn, in the county of Kings and State of New York, have invented certain Improvements in Artificial Lines, of which the following is a specification.

Thisinvention relates to an artificial line and more particularly it relates to an arti ficial line associated with a non-loaded cable circuit or a uniformly loaded cable. its object is to provide a simple circuit an. range-merit, consisting of condensers and non-inductive resistances which shall, over the range of frequencies essential for the telephonic transmission of speech, closely simulate in its electrical impedance, the characteristic impedance of the associated cable circuit.

The cable circuit with which the artificial line of m inven ion is adapted to cooperate, is characierizerl b relatively large distributed ca acity and relatively small uted inductance. As a consequence its impedance characteristics differ markedly from those of open wire lines or of ordinary loaded circuits. In previous inventions I have disclosed artificial lines adapted to simulate in their characteristic impcdauces open wire lines and loaded lines. My piesent invention consists of an artificiai line adapted to simulate in its impedance characteristics a non-loaded cable circuit or a uniformly loaded cable circuit, a. c. a cable in which the loading is uniformly distributed throughout t5 the. h of the cable instead of being lumped at suitable intervals, the artificial line being a simple electrical network con-- 1 uiniug a small number of elements.

My invention is capable of many and varied uses but is of particular uti ity as a balancing artificial line in two-way tworepeater circuits wherein the artificial line T ill ll: W I

' llifilZQEllL 1 moduli) ance components respectively of the characteristic impedance K; similarly A and B which it is associated.

distrib- Specification of Letters Patent.

Patented Sept. 18, 1917.

Serial No. 144,137.

must closely simulate the impedance characteristics of the transmission line with My invention is best understood by reference to the accompanying drawings in which Figure 1 is a diagram of the artificial line of my invention and Figs. 2, 3, 4, 5, 6 and 7 are plots of the impedance characteristics of cable circuits and of the artificial line.

Referring to Fig. 1 the artificial line will be seen to consist of two parts 1 and 2 serially connected between terminals 3 and 4. The part 1 comprises a non-inductive resistance element R in parallel with a second non-inductive resistance element R, and a. condenser (1,, while part 2 comprises a third non-inductive resistance element R in series with a second condenser C The artificial line is thus made up of five impedance elements only. The resultant impedance of the combination when the elements are proportioned, as hereinafter set forth "in this specification, with reference to the constants of the particular cable with which said line is to cooperate. closely simulates the impedance of the cable circuit over the range 0 frequencies necessary for the telephonic transmission of speech.

Proceeding now to derivation of the appropriate proportioning' of the artificial line, let K be the characteristic impedance of the cable circuit; R, L and C the distributed resistance, inductancennd capacity per unit length of said cable circuit, Z the unpedance of the part or portion 1 of the artificial line; Z, the impedance of the portion 2; 'ithe imaginary operatorJ 1; and p =21rf' where f is the frequency in cycles per second. The well known formulae for the impcdances K, Z aud'Z 1 then/given by the following equations:

are. hit m-;.n.-tance and rcactance components respectively f the impedance Z; and A and 13., the resistance and rcactance componcnts of the impedance Z In order thatthe artificial line shall simu- Equating real and imaginarv parts late the impledance K of the cable circuit it A 1 15 evident t at, for the telephtomcmange A m- -l -(1- (12) plus A must approximate value and B 6 plus B must approximate Q in value. To and 'this end the elements R R R 0 and C B 'w(lg) must be' proportioned with reference to the g flifl?" given values of R, L and C. In order to de- But by (8) rive the proper proportioning it is convend 10 ient to introduce certain parameters which (1 determine the values of the five impedance t elements .and which are themselves deter- Wheme mined by the characteristics of the actual B d cable. First let the symbol p be defined by f ffij j 1 l 4 p od- 001 B w p is 21:- times the frequency f below which o lmpedance'slmulanon 1s P yf In equations (12) and (13) u and 'u have 9 15 ge y to be taken p f "P- the values indicated by said equations. i proxirnetely 200 cycles per second, since he Further by reference to equation (3) it v quencles below this value are not necessary may b shown that for the telephonic transmission of speech;

A R Further let W: \V 18 clearly the :4 14 25 ratio of the freque cg f to the frequency f. u, tD0 I Now let the following equations define a. B 1 h set of parameters: dm fidm i (15) where n m 5) 1 h=-7 (16) e/ n OZJDO g-PC R (7) mg {3nd 0, are defined by equations (14) an a d"(1 9)t (8) 7 Equation (1) may be expressed By equation (2) KGDNiQ: Z 1 +tpQR, c

1 l since p 'wp. R: tD Further reduced this expression becomes whence TiTZ z L+', P,G1L K=D-Q= 2 p(l (j ED; P 1m0+ D I X/TZ 211T Substitute top for p and we get 211 it??? z 1+i-w '03,. 5R l- 60 {5; 1+twp' (R.,+ 21% 2 1Y)) But 10' C R fig by (7) and p (R +R PL o =1 by (4 whenee 1 mm R 55 mi? (11) Alsc ==D,, by equation (5) whence n Rationalizing (11) vve get 2( 1 Z +ie1 mi 2., i91'f 9 Th f w r so +t'w)(1-"iw) 1+w' 1+w From 2 Z==A- z'B. Substituting this -1) value for Z in the above equation we have o' real part of 2 r .0011'=-20.8, whence If a and b denote 2% and (T 0 0 respec tively b 'E% i aginary part( /2(ri (18) (lollectinglthe foregoing formulae and solving for t e five impedance elements,

so h 'dD,

The determination of the constants of the artificial line of my invention will now be given for the specific case where it is reuired that the artificial line shall simulate t e characteristic impedance of a cable cir cuit havingthe following constants, 3:203 ohms; L=.001.1 henry; 0=.0s55 1(r iarad. The first step is to decide on the value of p. In the present case it will be assumed that the impedance simulation is relatively unimportant for frequencies below 240 cycles per second, whence p :21: 1508 approximately. The" value L/R is b definition areas and by equation (5),

The next step is to substitute the value .08 for 1' in equations (17 and (1 and 45 to compute from said equations curves of 'a' and b with respect to w for different values of the parameters t and d respecand I) are illus of which is particular value of the param values of said. parameter extending from 11 .5 to d:

The third '0 as given Fig.

of curves each of which i ticular value of the parmne of said parameter ranging then by equation (1) a plot of equation 2.0. step is to plot grapl by equations (13) 4 is a plot of n+0 as ordin: W as filJSClSSiU, the figure fro:

Now it is evident from insperti tions (18),

the artificial line rcactance the reactance com istic impedance 0 must be closely eq of frequencies necessary (18) for n etei' (I. the

is of '1 and and (15 ites against showing a. family s a plot for a partcr It, the value on of equa- 13) and (15) that in order that onent of the sion. This range will be taken ing from 240 to values correspond to \V l and The next step is then to comspcctivel pare F1 gs.

ues of the parameters the plots Z1 and e+o are 2}, and 4 and to determine the 71 and (7 over the range of frequencies cor to the limits comparison of Figs. the choice ,of shows two curves, and the other that of e+u curves clearly cision with W=1 and W:10.

3 and one that of b for ficial line simulates that of the the specified ran e.

Having determine h and (1 parameters next step is to plot the ance of shall simulate churn eterthe cable circuit o-l-u, ual to 7) over the range for telephonic transas exten 2400 cycles per second, which W IO revulfor which most closely equal responding A detailed 4 leads-thus to h=.5 and d=1.2.

Fig. 5 for (1:12 h=.5; said show the high degree of pre which the react the art] cable over (1 the best values of the as illustrated above, the

values of u as ordinates against values of w as ahscissae for different values of the parameter of curves resulting are illustrated in Fig.

family plotted eter g.

approximate over the required range. the values of a in or sistance components the artificial be approximate 'er pendent of the frequency of the parameters (1 and.

dependent. 0

line and 2 and f the abscissaz w an the paramu-l-u must The from said plots 6, each curve being for a particular value of Now since the values of frequency do! that the re of the impedances of the cable circuit shall ncl, and since n is indethe proper values t are to be chosen a comparison of Figs. rameters being so chosen t between '11 an (i, the pahat the difl'crence a shall be approximately ind hence of the frequency. This at the same time determines the parameter s which is a-u. he parameters 5 and tare not independent since they are subject to the relation (i=6 (1-9) and hence a compromise value must be selected. For the particular example under consideration, I have chosen g=.2, t=l.5 and 8:.128 from a study of Figs. 2 and 6.

arin eters,

R =426 ohms R1=1O6 ohms R 54 ohms O =1.25 10-" farads C,=3.89 10 farads What is claimed is:

artificial line for simulatin the characteristic impedance of a cable circuit whose constants are uniformly distributed comprising a part consisting of and a non-inductive resistance in series with said condenser, and a sccon part serially connected with said first men ioned part and consisting of a second non-inductive resistance in parallel with the serial combinatlon of a second condenser and a third acteristic impedance-of the first art and the resistance com onent of the cl aracteristic impedance of t e second part approximates the resistance component of the characteristic impedance of the cable circuit, and the sum of the reactance com onents of the characteristic impedances o the two parts approximate the reactance component of the characteristic impedance of the cable circult.

2. An artificial line for simulatin the shunt part comprisin the elements 0 the r if -ial line being so proportioned that t the two parts shall respectively approximate the resistance and reactance components of the cable circuit.

In testimony whereof, I have signed my name to this specification in the presence of two subscribing witnesses, this 20th day of January 1917.

RAY S. HOYT. 

